Stabilized dioxolanes



Patented May 22, ms

STABILIZED DIOXOLANES William Franklin oi-eslism, Wilmlngtomlkb, asslgnor to E. I. du Pont de Nemours & Company. Wilmington, Del., a corporation of Delaware No Drawing. Application November 21, 1941, Serial No. 419,909

rcleim. (Cl. 260-2) 'l'his invention relates to a process for the stabilization of dloxolanes and more particularly to the treatment of polydioxolanes and their modiflcation products with antioxidants. I

Polydioxolane, obtained by the polymerization of 1,3-dioxolane by means of a catalyst or from other sources, as well as modified forms thereof resulting, for example, from the reaction of the polymer with acids, alcohols, esters, and the like have been found to be relatively unstable upon exposure to air or oxygen. This instability is more apparent in the higher molecular weight polymers and consequently uses based on the desirable characteristics of the polymers as prepared are restricted.

.An object of the present invention is to provide a process for stabilizing dioxolanes and modification products thereof. Another object is to provide antioxidants for 1,3-dioxolane and its modification products. Yet another object is to provide a process for making age-resistant ,polydioxolane, especially age-resistant high molecular weight polydioxolane and age-resistant high molecular weight polymeric modification products of polydioxolanes with organic acids, esters, alcohols, and the like. Other objects and advantages of the invention will hereinafter appear.

High molecular weight polydioxolane and high molecular weight modified products thereof, as

prepared, are tough, flexible resin-like products having considerable elasticity and high tensile strength. These properties are, however, not permanent for the compounds gradually lose these desirable properties after exposure to air or oxygen and become hard and brittle. It is believed that oxidation of the polymeric compounds is responsible for this phenomenon, although some polymers retain their flexibility and toughness for longer periods than others indicating that there are other contributing factors. Monomeric 1,3-dioxolane likewise deteriorates on exposure to air or oxygen, peroxides being formed which contaminate the monomer and limit the utility of the polymer made therefrom. It has been found that this aging and/or oxidation and/or peroxide formation can be inhibited and b in some instances entirely prevented by the use of antioxidants and more particularly by the use of non-volatile bases of the aromatic and heterocyclic series with two amino groups, or one amino and one hydroxyl group. Antioxidants generally which are eflective in the treatment of rubber, latex and the like are likewise suitable.

--; The polymers that can be stabilized in accord with this invention include the polymers of 1,3-

dioxolane as disclosed in U. S. application 8, N. 392,124, and more particularly the polymers of higher molecular weight obtained in accord with the process of that application such, for example, as those having a molecular weight from approximately 1000 to in the order of 200,000. Such olymers may be prepared from 1,3-dioxolane by contacting it with a catalyst such as sulfuric acid, or boron trifluorlde, preferably while under refiux. These polymers may likewise be prepared by' the interaction of a vicinal glycol, such as ethylene glycol, 1,2-propylene glycol, etc., with formaldehyde in the presence of similar catalysts, the reaction being conducted under reflux, the water formed as a result of the reaction being removed as formed. The products obtained from these reactions may be characterized as glycol formals and polyglycol formals specific members of the class being (methoxymethoxy) ethanol, CHaOCI-IaOCHzCHaOI-I; di(phydroxyethyl) formal, (HOCI-IzCHzQhCHz; methyl (pmethoxyethyl) formal, (CH)(CH:lOCH2CI-I20)CH2; ,s(methoxy-alpha-ethoxy) ethanol, omoono omcmon and similar glycol formals. Such a process. and

the products derivable therefromv are disclosed in U. S. application S. N. 392,125. High molecular weight products obtained in accord with the process described in U. S. application S. N. 392,126 may likewise be employed. The process of this application involves the reaction of vicinal glycols with formals using reaction conditions and catalysts above described, and in this instance in order to obtain the higher molecular weight polymers the alcohol formed as a result of the reaction is removed until a polymer of the desired molecular weight has been obtained. High molecular weight polymers obtained in accord with the process of U. S. application S. N. 392,126. may likewise be stabilized in accord with this invention, the products of this application being prepared by the treatment of compounds containing both a formal and an alcohol group such as di- (phydroxyethyl) formal, thereaction being carried out under the conditions specified above and U. S. application S. N. 392,124.

It is likewise possible to stabilize the products disclosed above which have been modified by combining them with other organic or inorganic compounds, such modified products being prepared by the interaction of, for example, the products of the above enumerated applications Serial Nos, 392,124; 392,125, and 392,126, with an alcohol, acid, ester. or other ouitobie modifying agents; the reoction being conducted by heating Amino or hydroxywompoundi:

Pcro bydroxydlpltlenyl Hydrodulnoue yoro umluophenol p,p-l)iominodipbenyimethonc 2,d-=meta.-toluylcne diomlne Secondary amides: Dlphcnylomine oand p-Dltolylomiuec Phenyl-ulpho-noplithylcmine Phenyl-beta-nophthylomino (Ncozonc" D) Phenyl=beto-nephthylnitrosamino Symmetrical di beta. nuphthyl pore phcnylenediomine (Ago-Rite White") Symmetrical diphenyldiomlnmethoue M-diominodipheuylumlue Londensotlon' products of omlnes with carbonyl compounds, e. 3.

OZ aniline with occtoldehydc.

E olpho-nophthylominc with oldol, Of aniline with o'cctone. dud.

OZ diphenylemine with acetone Qther antioxidants;

Glycollc aldehyde Glyoxel Hydroxy cldehydes from the condensation of formaldehyde with itself end especially the hydroxyoldehydes so prepared Reduclru, sugars Amino acid esters such as 'tryosine esters For use in the liquid monomeric and polymeric compounds metal antioxidants may be used, to prevent peroxide formation, such, for example, es copper, nickel, iron, etc.

The antioxidants other then the metals may be incorporated into the unpolymerized 1,3 dloxolone or its modification products prior or subsequent to polymerization and preferably in the amount ranging from 0.1 to 5.0 parts thereof by weight per 100 parts by weight of the dioxolane used, the monomeric mixtures bein then subjected to polymerization. The metals are merely placed in contact with the monomer, although the effectiveness of copper may be imcreased by reduction prior to use.

The examples of antioxidant treated and um treated polydioxolone which; follow illustrate the advantages of the invention.

To 320 parts of 1,3-dioxolane, which had. been purified by dlstiilatioufrom sodium hydroxide, was added .091 port of gaseous Br a and the mixture well agitated to insure uniform distribution otthe BF: in the 1,3-dioxolane. The mixture was allowed to stand at 6 C.'for '7 days. During this time the 1,3-dioxolane polymerized,

' in 300 parts of water containing 1 port oi cum ammonia. by stirring and worming. 0.03 port of sodium hydroxide was added to completely neutralize the BFa catalyst. The viscoueeolution was then heated to irom IE-90 C. at which point the polydioxolane become insoluble in the" water and separated as a. second blouse. The

\ clear supernatant liquid was poured oil and the and changed from a. mobile colorless liquid to 0.07

viscous mess of polydloxolane was poured on to glass plate to dry at room conditions. The film of poiydioxolone woe dry in 5 days.

l5. co ports or the polydioxolene was dieeolvcd in 309 parts of water containing 1 part of dour. emmonle by stlrrng and warming. Mid port o2 codium hydroxide was added to completely ncutrdlize the BFa catalyst. The viscous solution was then heated to from to out which point the polydioxolene becomes insoluble in the water and separated as a. second phase. The

\ cleor supernatant liquid was poured on leaving the polydioxolane as a. viscous mass. This rac terial was washed by redissolving in 3% parlc of water, heated to from 75 to 99 C. to reprecipitate the polymer and the clear supernctont wash water decanted. This washing process woe repeated until the wash water was neutral to litmus. The viscous polydioxolane was poured on to a. glass plate to dry. The film was dry in 5 days. I

C. 40 parts of polydioxolane woo worked up in exactly the some way as described in part B except that 2 ports of Neurone D (plienyl 'nephthyl amine) was added to the lost wash water. Thefllm was dry in 2 days.

D. 4.0 ports of polydioxolune wos worked up in exactly the some manner as part B except that 2 ports of Age-Rite White" was added to the last wash water. The film was dry in 2 days.

E. 46 parts of polydioxolane was worked up in exactly the some manner as part; B except that 2 parts of hydroquinone was added to the last wash water. The film was dry in 5 days.

All of the above polydioxolane films, when dry, were initially tough undpliable and could be cold drawn. The films from pdrte A and B after standing exposed to the atmosphereior 1 days had lost their initial toughness, pliability and ability to be cold drawn and had become weak and brittle. The films from parts 6,1). and E after standing exposed to the atmosphere for 90 days retained their toughness, pllability and ability to be cold drown.

From the examples given it is evident that the polymeric products which have been treated with an antioxidant are not subject to the rapid deterioration normally incident to the aging of the polymers not so treated. It should be noted, however, that polymerization of 1,3-dloxolone is conducted with acid catalysts which are neutralized subsequent to the reaction and accord,- ingly antioxidants which give colored decomposition products in alkaline solution should not be added priorto polymerization unless the discoloration is unobjectionable.

The antioxidants may be milled into or otherwise intimately incorporated with the solid polymer. Moreover, inasmuch as the oxidation of the solid polymers appears to be more or less a surface efi'ect gradually progressing into the center of the particular article or mass of the or its compounds or its modified products prior to polymerization, during polymerization, or subsequent thereto or to surface treatment with the antioxidant as a dry mixture containing it or as a solution thereof. The term polydioxolane compoun is likewise used in a generic sense and includes the 1,3-dioxolane polymers, their liquid or solid forms, their modification products described herein and in the specifications referred to; and to the polymeric glycol iormals, above described.

I claim:

Solid 1,3-dioxolane polymer; having a. molecular weight between 1,000 and 200,000, containing 0.1 to 5.0 parts of symmetrical di-beta-naphthyl-para-phenylenediamine per 100 parts of the polymer.

WILLIAM FRANKIE GRESHAM. 

